The greatness of Rome is often equated with its military power. In this, the Roman Legion is viewed as an essential innovation that evolved over the centuries, adapting itself to particular military challenges. Begun as an army of purely citizen-soldiers, the legion changed during the Republic to include landless volunteers as well as auxiliary troops. By the Imperial period, legions reflected the make-up of client-states and provinces, even including frontier barbarians.
Development of the Roman Legion
Like Greece, the geography of Italy imposed upon the Italian city-states the necessity of developing small fighting units along the lines of the Greek phalanx. These early units were comprised of citizen-soldiers, volunteers picked by their commanders. The term legere means “to collect” or pick.
After Rome’s initial defeat by the Samnites, military necessities resulted in the creation of the first legions. Often compared to a hand or fist, the legion, according to military historian Lynn Montross, was “capable either of closing up solidly like a fist, or of feeling out the enemy’s weaknesses…”
These early legions were composed of forty combat units, supported by light cavalry. Arranged in three lines, the legion’s first rank was made up of young, freshly trained men armed with spears (the Pilum) and swords (Gladius). The second rank was manned by seasoned troops while the third contained older veterans armed with javelins.
The legion was commanded by a consul who was assisted by six tribunes and sixty centurions. Ten cohorts of 420 men each comprised the legion’s infantry. With cavalry and reserve troops, this army typically totaled 10,000 men. The legion’s worth was aptly demonstrated against Pyrrhus in 281 BC.
Changes in the Roman Legion under Consul Marius
Gaius Marius served as consul an unprecedented seven times, during which he instituted significant changes to the legion. Historians frequently use the term “personal army” to designate the legions Marius equipped with his own money. Marius recruited landless men with the promise of future compensation in the form of land.
Forced to carry heavier packs, these legionnaires are often referred to as “Marius Mules.” Marius also improved the spear as well as more versatile uses of the standard legion battle plan. His generalship inspired respect that turned the loyalties of his soldiers from the state to Marius himself, creating fear and consternation in the Senate.
The End of the Republic and Caesar Augustus
Under Julius Caesar, the legions came to rely on allied auxiliary troops and reflected larger formations of heavy infantry and cavalry. Additionally, the Punic Wars had left valuable lessons in battle tactics, borrowed from Hannibal, such as flanking maneuvers and envelopment.
At the end of the Civil War in which Octavian defeated Marc Antony and Cleopatra, there were sixty legions throughout the empire. Augustus decreased the legions to 28 and the military became state-funded. Under Augustus, the expansion of Roman roads enabled swift dispersal of legions as they became needed during a crisis.
Historian Michael Grant, in noting the provincial character of many legions, states that Rome’s standing army, stationed throughout the empire, helped to expand trade and commerce while further “Romanizing” ancient communities. The residual effect was a self-sustaining Pax Romana.
By the 3rd Century, emperors used the military to achieve and maintain power and the cohesion of the legions began to decrease. Yet for five centuries the Roman legion, with few exceptions, had proven itself to be the most formidable military unit in the ancient world.
Sources:
- Mary T. Boatwright, Daniel J. Gargola, and Richard J. A. Talbert, The Romans From Village to Empire: A History of Ancient Rome from Earliest Times to Constantine (Oxford University Press, 2004)
- Martin Van Creveld, The Art of War: War and Military Thought (Cassell & Co. 2000)
- Michael Grant, History of Rome (Charles Scribner’s Sons, 1978)
- Lynn Montross, War Through the Ages 3rd Ed. (Harper & Row, 1960)
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